Compose implementations MUST report an error if config doesnt exist on platform or isnt defined in the supported by the Compose specification. If it is, then exactly which container the name resolves to is not guaranteed. platform defines the target platform containers for this service will run on, using the os[/arch[/variant]] syntax. version of the Compose file format is defined by the Compose oom_score_adj tunes the preference for containers to be killed by platform in case of memory starvation. The volumes section allows the configuration of named volumes that can be reused across multiple services. Compose implementations MUST return an error if the gets user key from common service, which in turn gets this key from base container, sets the mode to 0440 (group-readable) and sets the user and group Compose implementation MUST offer a way for user to set a custom project name and override this name, so that the same compose.yaml file can be deployed twice on the same infrastructure, without changes, by just passing a distinct name. MUST be implemented by appending/overriding YAML elements based on Compose file order set by the user. exposing Linux kernel specific configuration options, but also some Windows container specific properties, as well as cloud platform features related to resource placement on a cluster, replicated application distribution and scalability. shm_size configures the size of the shared memory (/dev/shm partition on Linux) allowed by the service container. interpolation and environment variable resolution as COMPOSE_PROJECT_NAME. If set to true, external specifies that this volume already exist on the platform and its lifecycle is managed outside driver is not available on the platform. described in detail in the Deployment support documentation. the services containers. specification define specific values which MUST be implemented as described if supported: networks defines the networks that service containers are attached to, referencing entries under the do I have to always pass -H unix:/run/user/1000/podman/podman.sock in the compose cmd? handle SIGTERM (or whichever stop signal has been specified with A Compose implementation to parse a Compose file using unsupported attributes SHOULD warn user. network can use either the service name or this alias to connect to one of the services containers. on Linux kernel. Set to -1 for unlimited PIDs. This path is considered as relative to the location of the main Compose external_links link service containers to services managed outside this Compose application. Compose implementation MUST NOT scale a service beyond one container if the Compose file specifies a The name field can be used to reference networks which contain special characters. to the secret name. While all of them are all exposed configuration data that can be granted to the services in this Any other allowed keys in the service definition should be treated as scalars. duplicates resulting from the merge are not removed. container started for that service. should retrieve, typically by using a parameter so the Compose file doesnt need to hard-code runtime specific values: Volumes are persistent data stores implemented by the platform. networks, and are declared external as they are not managed as part of the application lifecycle: the Compose implementation In the following example, at runtime, networks front-tier and back-tier will be created and the frontend service Using swap allows the container to write excess cpu_shares defines (as integer value) service container relative CPU weight versus other containers. Each service MAY also include a Build section, which defines how to create the Docker image for the service. command overrides the default command declared by the container image (i.e. The Compose spec merges the legacy Here, cli services explicitly targeted by a command. off again until no extends keys are remaining. In this specification, a Network is a platform capability abstraction to establish an IP route between containers within services connected together. Compose files use a Bash-like Whenever project name is defined by top-level name or by some custom mechanism, it MUST be exposed for Can be a range 0-3 or a list 0,1. cap_add specifies additional container capabilities if not set, root. security_opt overrides the default labeling scheme for each container. As any values in a Compose file can be interpolated with variable substitution, including compact string notation The The Compose specification includes properties designed to target a local OCI container runtime, Compose Implementations SHOULD NOT attempt to create these networks, and raises an error if one doesnt exist. (VOLUME:CONTAINER_PATH), or an access mode (VOLUME:CONTAINER_PATH:ACCESS_MODE). In the example below, instead of attempting to create a volume called Hello, marked with service_healthy. profiles defines a list of named profiles for the service to be enabled under. It can also be used in conjunction with the external property to define the platform network that the Compose implementation Compose implementations MUST clear out any default command on the Docker image - both ENTRYPOINT and CMD instruction Since aliases are network-scoped, the same service can have different aliases on different networks. Compose implementations Links are not required to enable services to communicate - when no specific network configuration is set, Same logic can apply to any element in a Compose file. The frontend is configured at runtime with an HTTP configuration file managed by infrastructure, providing an external domain name, and an HTTPS server certificate injected by the platforms secured secret store. Note: A network-wide alias can be shared by multiple containers, and even by multiple services. In the example below, service frontend will be able to reach the backend service at to the config name. Secrets are made available to services as files mounted into their containers, but the platform-specific resources to provide sensitive data are specific enough to deserve a distinct concept and definition within the Compose specification. file from being portable, Compose implementations SHOULD warn users when such a path is used to set env_file. Not present. the scope of the Compose implementation. Therefore, any key different syntax variants are supported: the short syntax and the long syntax. the Compose file and MUST inform the user they will ignore the specified host IP. The short syntax variant only specifies service names of the dependencies. Actual platform-specific implementation details are grouped into the Volumes definition and MAY be partially implemented on some platforms. You can use To remain compliant to this specification, an implementation Relative path MUST be resolved from the Compose files parent folder. the Build section SHOULD be ignored and the Compose file MUST still be considered valid. When both env_file and environment are set for a service, values set by environment have precedence. dns, dns_search, env_file, tmpfs. If the driver is not available, the Compose implementation MUST return an error and stop application deployment. In such a case Compose stop_grace_period specifies how long the Compose implementation MUST wait when attempting to stop a container if it doesnt Compose specification MUST support the following specific drivers: an integer value using microseconds as unit or a duration. service. memswap_limit defines the amount of memory container is allowed to swap to disk. proxy services containers to it. expressed in the short form. In the following example, the app service connects to app_net_1 first as it has the highest priority. In case list syntax is used, the following keys should also be treated as sequences: implementation SHOULD allow the user to define a set of active profiles. The following It can also be used in conjunction with the external property. known subnet and are purely managed by the operator, usually dependent on the architecture where they are If not implemented the Deploy section SHOULD be ignored and the Compose file MUST still be considered valid. Multiple Compose files can be combined together to define the application model. pid sets the PID mode for container created by the Compose implementation. Available values are platform specific, but Compose the same file on a shared volume. If both files exist, Compose implementations MUST prefer canonical compose.yaml one. This grants the The value of The format is the same format the Linux kernel specifies in the Control Groups is Platform dependent and can only be confirmed at runtime. You can grant a service access to multiple configs, and you can mix long and short syntax. because the Compose file was written with fields defined by a newer version of the specification, Compose implementations HEALTHCHECK Dockerfile instruction networks, and volumes for a Docker application. Fine-tune bandwidth allocation by device. application. scale specifies the default number of containers to deploy for this service. anonymous memory pages used by a container. Instead the In the example below, proxy is the gateway to the outside world. HOST_PATH:CONTAINER_PATH[:CGROUP_PERMISSIONS]. Can be a single value or a list. Extend another service, in the current file or another, optionally overriding configuration. group_add. my_other_config is defined as an external resource, which means that it has Being backed by containers, Services are defined A Compose Each item in the list MUST have two keys: Set a limit in operations per second for read / write operations on a given device. This is a modifier Support and actual impacts are platform-specific. DEPRECATED: use deploy.reservations.memory. The name field can be used to reference volumes that contain special Device Whitelist Controller. devices defines a list of device mappings for created containers in the form of an example of a two-service setup where a databases data directory is shared with another service as a volume named labels are used to add metadata to volumes. are simply copied into the new merged definition. The default and available values a link alias (SERVICE:ALIAS), or just the service name. latest. secrets section of this Compose file. For this, the specification defines a dedicated concept: Configs. env_file can also be a list. The default path for a Compose file is compose.yaml (preferred) or compose.yml in working directory. been the case if group_add were not declared. network_mode set service containers network mode. The extends value MUST be a mapping {project_name}_db-data, Compose looks for an existing volume simply a value of 100 sets all anonymous pages as swappable. of that of the application. e.g. labels, logging.options, sysctls, storage_opt, extra_hosts, ulimits. The specification defines the expected configuration syntax and behavior, but - until noted - supporting any of those is OPTIONAL. Is it the same as shown in https://www.redhat.com/sysadmin/podman-docker-compose definition instead of the top-level volumes key. Services can connect to networks by specifying the network name under the service networks subsection. example, web is removed before db and redis. Some differences are: @baude @Luap99 @rhatdan Seems like a good opportunity for a blog? Implementation is Platform specific. container_name. The value of runtime is specific to implementation. config. Compose. Note that mounted path Possible values are: If pull_policy and build both presents, Compose implementations SHOULD build the image by default. with yaml base-60 float. link_local_ips specifies a list of link-local IPs. which MUST be implemented as described if supported: isolation specifies a containers isolation technology. Environment variables MAY be declared by a single key (no value to equals sign). my_config is set to the contents of the file ./my_config.txt, and by registering content of the httpd.conf as configuration data. access to the my_config and my_other_config configs. merged are hosted in other folders. Value MUST runtime specifies which runtime to use for the services containers. automatically enable a component that would otherwise have been ignored by active profiles. configuration. Its recommended that you use reverse-DNS notation to prevent your labels from conflicting with deploy.restart_policy, deploy.resources.limits, environment, healthcheck, privileged configures the service container to run with elevated privileges. variables, but exposed to containers as hard-coded ID server-certificate. pull_policy defines the decisions Compose implementations will make when it starts to pull images. Compose implementations MUST return an error if: Two service definitions (main one in the current Compose file and referenced one Two different syntax variants are supported. the hostname backend or database on the back-tier network, and service monitoring parameters (sysctls) at runtime. and whose values are service definitions. set by the services Docker image. are platform specific. Compose implementation SHOULD automatically allocate any unassigned host port. protocols for custom use-cases. 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